Reconfiguration of Active Component Carrier Set in Multi-Carrier Wireless Systems

ABSTRACT

In a multi-carrier wireless system, potential problems from reconfiguring mobile station resources to accommodate changes in component-carrier configuration are mitigated by inserting a guard period each time the configuration of component carriers changes, so that transceiver reconfiguration can be carried out without interfering with ongoing transmission. A base station is configured to transmit data to a mobile station according to a first configuration of two or more component carriers, to determine that a change of configuration to a second component-carrier configuration is required, and to signal the change of configuration to the mobile station, using the first configuration of component carriers. The base station then refrains from transmitting data to the mobile station during a pre-determined guard interval of at least one transmission-time interval subsequent to the signaling of the change of configuration. After the guard interval, data is transmitted to the mobile station according to the second component-carrier configuration.

RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 13/498,195 filed Mar. 26, 2012, which is a U.S. national stageapplication under 35 U.S.C. §371 of International Patent Application No.PCT/SE09/51484 filed Dec. 22, 2009, which claims priority to U.S.Application No. 61/247,086 filed Sep. 30, 2009.

TECHNICAL FIELD

The present invention is related to wireless communications systems, andin particular is related to the operation of mobile stations and basestations in a multi-carrier wireless system, in which data can betransmitted to or from a mobile station using two or more distinct,separately modulated, carrier frequencies.

BACKGROUND

Forthcoming cellular system standards, such as the so-called “Long-TermEvolution” (LTE) systems developed by participants in the3<rd>-Generation Partnership Project (3GPP), will provide a much largerdegree of flexibility than currently operating wireless networks. Inparticular, systems deployed according to Release 10 of the 3GPP LTEspecifications will be better able than existing systems to exploit thefull potential of the new technologies introduced in LTE, both in termsof system and per-user throughput, and will be better suited forco-existence and deployment in legacy bands.

A mobile station (a user equipment, or UE, in 3GPP terminology) designedfor such future standards will generally be required to support a widerange of bandwidths, in many cases aggregated within or over multiplebands. Carrier aggregation, in which two or more separately modulatedcarrier signals in distinct frequency bands are simultaneously used tocarry uplink or downlink traffic for a given mobile station, may beviewed as a scheme for providing flexible bandwidth configuration on asub-frame basis. With this dynamic re-allocation of potentially largechunks of bandwidth, future systems will be able to quickly respond tousers' varying needs for data transmission throughput.

In such a multi-carrier system, such as for an LTE release-10 connectionbetween a network and mobile station, there will be an active set ofcarriers that are available for carrying traffic for that mobile; thesecarriers are referred to as component carriers. The mobile station willnot be required to continuously receive and transmit on all componentcarriers in the active set—a given component carrier needs to beprocessed by the mobile station's receiver or transmitter only if thereis a data transmission assignment or grant for that component carrier.

Generally, multiple component carriers need to be simultaneously usedfor a given mobile station only if those data transmissions are frequentand large enough. As a result, discontinuous-reception (DRX) anddiscontinuous-transmission (DTX) mechanisms will be used to allow themobile station to power down parts of the receiver and transmitterduring times when no data needs to be received or transmitted on one ormore of the component carriers in the active set—this approach allowsfor a dramatic reduction in power consumption when data throughputrequirements are very low or moderate, compared to the power consumedduring maximum throughput scenarios, i.e., when all of two or moreavailable component carriers are fully utilized. Indeed, the use of suchschemes is generally considered to be a prerequisite to obtain anacceptable level of power consumption in multi-carrier-capable mobilestations.

In the standardization of multi-carrier operation in LTE release 10, theexact operation of DRX and DTX has not yet been specified. Inparticular, issues regarding whether and how DRX and DTX for onecomponent carrier will relate to DRX and DTX for other componentcarriers has not been resolved. One possibility is that all componentcarriers always follow the same DRX/DTX cycle. An alternative approachthat provides a greater degree of flexibility is to permit eachcomponent carrier to have its own independent DRX/DTX cycle.

SUMMARY

In a multi-carrier system, discontinuous receive (DRX) and discontinuoustransmit (DTX) processes need to be predictable well in advance ofchanges in component-carrier configuration, to allow for carefulscheduling of power-down, power-up and/or reconfiguration of transceivercomponents. This careful scheduling is necessary to avoid interferingwith the ongoing reception and transmission. This scheduling isparticularly complicated in multi-carrier systems because the numberand/or identities of component carriers scheduled for a given intervalmay vary from one sub-frame to the next, often in ways that areunpredictable.

Accordingly, in various embodiments of the present invention, potentialproblems from reconfiguring mobile station resources to accommodatechanges in component-carrier configuration are mitigated by inserting aguard period each time the configuration of component carriers changesdue to an inter-component-carrier assignment, so that power-up/downand/or radio reconfiguration can be carried out without interfering withongoing transmission. In other words, a guard period corresponding to atleast one subframe is inserted prior to configuration changes to allowfor power-up, power-down, and/or radio reconfiguration events. It isreadily understood that the duration of this guard period could be oneor several transmission time intervals.

Embodiments of the present invention comprise base stations and mobilestations, each configured to exploit a guard interval accompanyingchanges of component-carrier configuration. Corresponding methods foroperating a base station and a mobile station are also disclosed. Forexample, an exemplary base station according to some embodiments of theinvention comprises a control circuit configured to transmit first datato a mobile station according to a first configuration of two or morecomponent carriers, to determine that a change of configuration to asecond component-carrier configuration is required, and to signal thechange of configuration to the mobile station, using the firstconfiguration of component carriers. The control circuit is furtherconfigured to then refrain from transmitting data to the mobile stationduring a pre-determined guard interval of at least one transmission-timeinterval subsequent to the signaling of the change of configuration.After the guard interval, the control circuit then transmits second datato the mobile station according to the second component-carrierconfiguration.

In some embodiments, the pre-determined guard interval consists of asingle transmission-time interval, such as an LTE subframe, althoughother guard interval lengths are possible. The precise timing of theguard interval may also vary, depending on the embodiment—in someembodiments, the pre-determined guard interval immediately follows thetransmission-time interval in which the change of configuration issignaled, while in others, the guard interval is delayed by one or moretransmission-time intervals following the transmission-time interval inwhich the change of configuration is signaled. In the latter case, thebase station may continue transmitting the first data according to thefirst configuration for at least one transmission-time intervalsubsequent to the signaling of the change of configuration and prior tothe pre-determined guard interval.

Several different changes to component-carrier configuration may triggerthe operations summarized above. For instance, in some embodiments thetriggering change in configuration may be limited to a change in thenumber of component carriers to be used for data transmission, while inother embodiments, any change to the set of active component carriersmay trigger the use of a guard interval, including those changes wherethe number of active component carriers remains the same.

Because the scheduling of the guard interval may coincide with one ormore previously scheduled processes from time to time, the base stationmay be further configured to automatically adjust those processes toaccommodate the guard interval, or to mitigate the guard interval'seffect. For instance, in some embodiments, the base station may befurther configured to delay an automatic-repeat-request processcorresponding to the mobile station by a number of transmission-timeintervals equal to the pre-determined guard interval.

An exemplary wireless mobile station configured for multi-carrieroperation according to the techniques disclosed herein comprises acontrol circuit configured to receive first data from a base stationaccording to a first configuration of two or more component carriers andto receive signaling information indicating that a change ofconfiguration to a second component-carrier configuration is pending. Inresponse to the signaling information, the wireless mobile stationselectively activates de-activates or reconfigures one or moretransceiver components during a pre-determined guard interval of atleast one transmission-time interval, and then receives second data fromthe base station according to the second component-carrierconfiguration, after the expiry of the guard interval.

Again, the pre-determined guard interval may consist of a singletransmission-time interval, in some embodiments, although other guardintervals are possible. Likewise, while in some embodiments thepre-determined guard interval immediately follows the transmission-timeinterval in which the signaling information is received, in otherembodiments the guard interval is instead delayed by one or moretransmission-time intervals following the transmission-time interval inwhich the change of configuration is signaled; in these latterembodiments the mobile station may continue receiving the first dataaccording to the first configuration for at least one transmission-timeinterval subsequent to receiving the signaling information and prior tothe pre-determined guard interval.

As was the case with the base station discussed above, a wireless mobilestation configured according to the present invention may be furtherconfigured to adjust one or more already scheduled processes toaccommodate the guard interval accompanying a component-carrierconfiguration change. For instance, in some embodiments the mobilestation is further configured to delay an automatic-repeat-requestprocess corresponding to the mobile station by a number oftransmission-time intervals equal to the pre-determined guard interval.In these and other embodiments, the mobile station may be furtherconfigured to determine that an outgoing data transmission is scheduledfor the guard interval and to defer the data transmission until afterthe pre-determined guard interval. In some embodiments, this deferral ofthe data transmission until after the pre-determined guard interval maycomprise performing a HARQ retransmission of the outgoing datatransmission.

Methods corresponding to the various base station and mobile stationsembodiments summarized above are also disclosed. Of course, thoseskilled in the art will appreciate that the present invention is notlimited to the above features, advantages, contexts or examples, andwill recognize additional features and advantages upon reading thefollowing detailed description and upon viewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a timing diagram illustrating effects of a component-carrierconfiguration change on a wireless receiver.

FIG. 2 is another timing diagram illustrating the use of a guardinterval according to some embodiments of the present invention.

FIG. 3 illustrates functional elements of an exemplary base station andan exemplary wireless receiver.

FIG. 4 is a process flow diagram illustrating an exemplary method forcontrolling data transmission in a multi-carrier wireless network.

FIG. 5 is a process flow diagram illustrating a corresponding method forcontrolling receiver operation in a multi-carrier wireless network.

DETAILED DESCRIPTION

The introduction to wireless systems of carrier aggregation, i.e.,multi-carrier operation, calls for mobile stations having theflexibility to reconfigure their radio transceiver resources dependingon which component carriers (CC) are active (i.e., actually orpotentially carrying control and/or traffic data for that mobilestation) at a given point in time. A brute-force transceiver designmight have multiple and independent transceiver entities, e.g., one foreach carrier or perhaps one for each set of contiguous carriers. Moreelaborate receiver and transmitter architectures that are specificallytailored for carrier aggregation may be unable to reconfigure on aper-CC basis, because some transceiver parts are shared for theprocessing of several carriers. However, still more sophisticateddesigns may allow the selective activation, deactivation, orreconfiguration of various receiver and/or transmitter components inresponse to dynamic changes in the configuration of component carriers,to minimize power consumption.

A potential problem with multi-carrier receiver/transmitter designsstems from the fact that events such as power-up, power-down, orreconfiguration of some blocks of a transceiver may not be acceptablewhile data is being received or transmitted on any carrier. Such events,even if they are carried out with respect to blocks that are notcurrently being used for transmission and/or reception, may neverthelessinterfere with the operation of active blocks.

One reason for this is that such events can generate transient responses(voltage and current spikes, voltage offsets, etc.) that may be coupledto devices and nodes of active blocks through various means, including,but not limited to, voltage/current supply wires and traces, capacitiveand inductive coupling, substrate coupling, and thermal coupling.Coupling of these transient responses to active functional blocks of thetransceiver may interfere with ongoing transmission and reception. Thisinterference may be direct, e.g., via coupling to nodes and devicesoperating on the desired signals, or indirect, e.g., via coupling tonodes and devices that control the behavior (gain, transfer function,oscillation frequency etc.) of active functional blocks, or both.

If all scheduling of component carriers is known sufficiently in advanceof any changes in component-carrier configuration, this problem can bereduced by simply activating, de-activating, or re-configuringtransceiver components ahead of time, during an interval in which nodata is being received or transmitted. However, the allocation ofcomponent carriers in multi-carrier systems may not be that predictable.For example, in LTE standardization discussions it has been proposedthat a first downlink component carrier can contain an assignment, for agiven mobile station, referring to a second component carrier that waspreviously not being used to carry data for the mobile station. Thisresults in a change of component-carrier configuration that cannot bepredicted ahead of time such that power up/down and/or radioreconfiguration can be scheduled without interfering with ongoingtransmission.

The discussion that follows is based generally on terminology andoperation of 3GPP LTE systems, and in particular discusses aspects of3GPP LTE release 10. However, those skilled in the art will appreciatethat the inventive techniques described herein are by no means limitedto LTE systems or to 3GPP-specified systems. Rather, the inventivetechniques described below may be applied to any system supporting acarrier aggregation scenario where a varying number of componentcarriers are received and/or transmitted more-or-less discontinuously.

In the time domain, a component carrier transmission may be divided intosub-frames, where a subframe represents the largest entity in time thatcannot generally be broken into smaller discontinuous pieces oftransmission (unless, perhaps, only control data is sent). In LTE, thesub-frames consists of a number of contiguous OrthogonalFrequency-Division Multiplexing (OFDM) symbols. Between any twocontiguous OFDM symbols or sub-frames there is no explicit guard periodallowing for a change of transceiver operation mode. There is, however,a so-called cyclic prefix (CP) at the beginning of every OFDM symbol toreduce channel-induced inter-symbol interference. Depending on theactual implementation of a transceiver, it is conceivable that all orpart of the CP could be used for reconfiguration or power up/down ofindividual blocks, so that reconfiguration of the transceiver toaccommodate changes in component-carrier configuration can be carriedout without impairing the transceiver's performance. Unfortunately, inmost cases the CP is orders of magnitude shorter than would be neededfor this purpose (typically some 5 us in LTE). As a result, thisapproach is simply not practical.

A mobile station transceiver configured according to some embodiments ofthe present invention supports carrier aggregation for the uplink (TX),downlink (RX), or both. To fully exploit the potential for reduced powerconsumption made possible by the techniques discussed below, thetransceiver should have one or more components or functional blocks thatcan be selectively activated, de-activated, or reconfigured, dependingon how many and/or which component carriers are being processed. Somesuch transceivers may be divided into a number of distinct transmitterand/or receiver units where each such unit is used to process at leastone component carrier (CC). Alternative or additionally, a mobilestation transceiver may have units (e.g., individual components orgroups of components acting as a functional block) that can bereconfigured to handle varying numbers of component carriers, withvarying power consumption. These units may be any sort of block orcombination of blocks typically found in a transceiver, includingamplifiers, filters, mixers, ADCs, DACs, PLLs, digital circuitry, etc.The purpose of introducing this partitioning or flexibility is to allowfor a more power efficient operation of the transceiver as the number ofCCs and their properties change.

Generally speaking, the basic building blocks of receivers andtransmitters differ with respect to the time it takes to change the modeof operation, e.g., the time it takes to power-up, power-down, orreconfigure a block. Typically, the phase-locked loop (PLL) circuitsresponsible for synthesizing local oscillator signals used for frequencytranslation are the circuits that take the longest time to start-up orreconfigure—this time may be on the order of some 100 microseconds fromcold start to stable output. Filters, on the other hand, naturally haveassociated time constants related to the bandwidth of the filters, butthese time constants are typically much smaller than those associatedwith a PLL circuit. Other blocks like amplifiers, mixers, etc., may haveno intrinsic time constant of significance, at least not with respect totheir signal paths. Nevertheless, even these blocks may need asubstantial amount of time to reach stable operation simply becausethere are time constants associated with power supply, biasing, anddecoupling networks. Some blocks may, however, have a change of mode ofoperation duration that is of no practical importance, e.g., digitalcircuitry and switching of signals.

Discontinuous receive (DRX) and discontinuous transmit (DTX) mechanismsare generally well known, and serve as the basis to enable regularlyturning off the receiver and transmitter, respectively, or partsthereof, when the data throughput is small or zero. While it isstraightforward to schedule power-up and power-down events for thesingle-carrier case based on the known DRX/DTX cycles for the singlecarrier, the situation becomes more complicated for a transceiversupporting carrier aggregation. In this latter case, power-up andpower-down of any block may need to be scheduled not only based on thecarrier to be processed but also with respect to the activity of allother carriers, for the reasons discussed above.

In some cases, the discussion that follows will be limited, for the sakeof clarity, to DRX cycles and to a mobile station's receiver(s).However, those skilled in the art will appreciate that correspondingscenarios and proposed procedures can be applied to DTX and the mobilestation's transmitter side instead, or to the combined operation ofreceivers and transmitters.

FIG. 1 illustrates a scenario including two receive CCs, i.e., twodownlink component carriers in the mobile station's active set ofcomponent carriers. At the beginning of the time frame illustrated inFIG. 1, there is no data for transmission, and thus both componentcarriers are inactive. However, CC#1 has a predictable active period onsubframe 3 (e.g., according to a periodic DRX cycle), and therefore therequired parts of the transceiver can be powered-up and configured forreception of CC#1 well ahead of time, say in subframe 2. Thus, theactivation of transceiver components to handle the reception of CC#1 insubframe 3 doesn't interfere with the transmission in any way.

Given such predictability of downlink transmissions, active blocks (AB)and non-active blocks (NAB) in time can be defined, where each ABdefines a period in time where no detrimental power up/down and/or radioconfiguration should take place. Thus, power-up/down and radioconfiguration should preferably be scheduled only in non-active blocks(NABS).

But in the pictured scenario, the downlink in subframe 3 of CC#1contains an inter-CC assignment referring to CC#2 in the next subframe.In other words, the mobile station learns during subframe 3 that it mustbe prepared to receive CC#2 by the start of subframe 4. If portions ofthe transceiver have previously been de-activated, this inter-CCassignment may require a power-up and/or reconfiguration of parts of thetransceiver to accommodate the reception of CC #2. However, since thisrequirement could not have been predicted ahead of time, there is no NABwhere it can take place without potentially interfering with the ongoingreception. This is seen in the figure, which indicates when thetransceiver blocks associated with CC#1 and CC#2, respectively, can bepowered up. Because the power-up of blocks associated with receivingCC#2 can only be powered up during subframe 3, this power-up activity ispotentially detrimental to the ongoing reception of data from CC#1.

To avoid this problem, a new technique for handling component carrier(CC) set reconfiguration is disclosed herein. According to severalembodiments of the invention, the mobile station and the base station(evolved node B, or eNodeB, in 3GPP terminology) are each configuredaccording to the following rule: if signaling in subframe k indicates asubsequent change in component-carrier configuration, relative to thestatus at subframe k, then at least one subsequent subframe (e.g.,subframe k+1 to subframe k+x, where x>0) should not be used for anysignaling or traffic data for or from that mobile station. In otherwords, a guard interval of at least one subframe (or othertransmission-time interval) is inserted between the indication of achange in configuration and the initiation of signaling or datatransmission according to that new configuration.

FIG. 2 illustrates an inter-component-carrier assignment where the basestation performs scheduling according to one embodiment of thisapproach. As was the case in FIG. 1, signaling received via CC #1 atsubframe 3 indicates that the mobile station should activate componentcarrier #2, to receive traffic data or to monitor control channelsignaling, or both. However, unlike the scenario illustrated in FIG. 1,a guard interval of one subframe is inserted first (at subframe 4), sothat component carrier #2 becomes active beginning at subframe 5. Thisprovides an opportunity to power-up any necessary receiver circuitry (orre-configure active circuitry) during subframe 4, such that the power-updoes not interfere with data reception on any of the active channels.

As suggested above, the guard interval may be one or several subframes(or other transmission-time interval, in systems other than LTE).Further, although the guard interval is shown in FIG. 2 as immediatelysucceeding the interval in which the configuration change is signalled,the guard interval could be delayed by one or more subframes in someembodiments.

Since the eNodeB in an LTE system controls the scheduling of datatransmissions, those skilled in the art will appreciate that in someembodiments it may be sufficient that the eNodeB is configured accordingto the appropriate “rule” for inserting guard intervals, with the mobilestation simply activating or de-activating component carriers as itreceives scheduling information. In other embodiments, however, mobilestations may be specifically configured to follow the same rule, tomaintain synchronization with the base station.

In some embodiments, the DRX (or DTX) procedure is configured so that aguard interval is inserted for any change in component-carrierconfiguration, including those changes where the active set of componentcarriers remains the same size. In other embodiments, dynamiccomponent-carrier-configuration changes may be limited to a change inthe number of component carriers that are used from one period toanother, such as from a single component carrier to two componentcarriers, and back again. In some embodiments, then, a guard intervalmay be inserted in response to an indication that the number ofcomponent carriers to be used in a subsequent subframe is changing. Inother embodiments, a more generalized technique may be used that takesinto account that the number of component carriers may remain the samewhile the set of active component carriers changes.

Embodiments of the invention thus include a base station (e.g., an LTEeNodeB) configured to selectively transmit control data and/or trafficdata to a given mobile station over one or several of two or morecomponent carriers. Some embodiments may also (or instead) be configuredto receive data and/or traffic data from a given mobile station over oneor several of two or more component carriers. In either case, theconfiguration of active component carriers (i.e., component carriersthat may carry control data or traffic data, or both, from or to themobile station) may change on a fast basis (e.g., via PDCCH signaling inan LTE system). A functional block diagram of one such embodiment ispictured in FIG. 3, which illustrates an eNodeB 310, comprising radiocircuits 312 and signal processing and control circuits 314, which inturn include a scheduler 316 for planning and coordinating uplink anddownlink transmissions between the eNodeB 310 and one or more mobilestations (including UE 320, in FIG. 3.)

To facilitate the use of at least partly independent DRX (and/or DTX)state machines for each component carrier, a base station according tosome embodiments of the present invention is further configured to carryout the process illustrated generally in FIG. 4. Thus, as shown at block410, the base station is configured to transmit control data and/ortraffic data to the mobile station according to a firstcomponent-carrier configuration. After determining that acomponent-carrier-configuration change is needed, as indicated at block420, the base station signals the required configuration change to themobile station, as illustrated at block 430. Of course, the change inconfiguration has not yet occurred, so this signaling is carried outusing the first component-carrier configuration.

As discussed above, the change in component-carrier configuration may bedelayed by several transmission-time intervals, in some embodiments.Thus, in some embodiments, data may continue to be transmitted accordingto the first component-carrier configuration for one or moretransmission-time intervals following the signaling of a configurationchange, as illustrated in FIG. 440.

In any case, however, a pre-determined guard interval of at least onetransmission-time interval is introduced at some point after thesignaling of a configuration change, during which guard interval thebase station refrains from transmitting data. This is illustrated atblock 450 of FIG. 4. As discussed at length above, this allows themobile station adequate time to reconfigure its transceiver resources toeliminate or mitigate adverse consequences that might otherwise resultfrom the powering-up, powering-down, or reconfiguring of radio resourceswhile simultaneously receiving data. After the guard interval hasexpired, transmission of control data and/or traffic data according tothe changed component-carrier configuration resumes, as shown at block460.

Other embodiments of the invention include a mobile station configuredto selectively receive control data and/or traffic data from a basestation over one or several of two or more component carriers. Someembodiments may also (or instead) be configured to transmit data and/ortraffic data over one or several of two or more component carriers. Ineither case, the configuration of active component carriers (i.e.,component carriers that may carry control data or traffic data, or both,from or to the mobile station) may change on a fast basis (e.g., viaPDCCH signaling in an LTE system). Referring back to FIG. 3, afunctional block diagram of one such exemplary mobile station configuredaccording to the inventive techniques disclosed herein is pictured. Theillustrated mobile station comprises radio circuits 322 and basebandprocessing and control circuits 324, which in turn include a DRX/DTXcontroller 326, which handles, among other things, the scheduling andcontrolling of radio resources according to scheduling informationreceived from eNodeB 310. Thus, DRX/DTX controller 326 generates controlsignals that activate, de-activate, and/or re-configure portions of theradio circuits 322 as needed, depending upon downlink/uplink resourcegrants, active DRX/DTX cycles, and the current component-carrierconfiguration.

To facilitate the use of at least partly independent DRX (and/or DTX)state machines for each component carrier, a mobile station according tovarious embodiments of the present invention is further configured tocarry out the method illustrated generally in FIG. 5. Thus, as shown atblock 510, the mobile station first receives control data and/or trafficdata from the base station according to a first component-carrierconfiguration. At some point, the mobile station receives signalinginformation indicating that a component-carrier-configuration change ispending, as indicated at block 520.

As discussed above in connection with FIG. 4, the actual configurationchange indicated may be deferred by one or more transmission-timeintervals following the signaling of the change—the length of thisdeferral may be pre-determined, in some embodiments, or included in thesignaling information, in others. Accordingly, in some embodiments ofthe invention, the mobile station may continue to receive datatransmitted according to the first component-carrier configuration forone or more transmission time intervals following the signaling of aconfiguration change, as shown at block 530. Whether immediately afterthe signaling, or several transmission-time-intervals later, however, apre-determined guard interval is scheduled in response to the signalinginformation. During this guard interval, the mobile station's controlcircuitry (e.g., the DRX/DTX controller 326 of FIG. 3) selectivelyactivates, de-activates, and/or reconfigures one or more receivercircuits, as shown at block 540. The particular receiver circuits thatare activated, de-activated, or re-configured are selected based on thecomponent-carrier-configuration change; thus the signaling informationis used to determine which receiver circuits are affected. Finally,after expiry of the guard interval, reception of control data and/ortraffic data is resumed, but according to the changed component-carrierconfiguration. This is illustrated at block 550.

Those skilled in the art will appreciate that insertion of a guardinterval according to the techniques described above may have an impacton automatic-repeat-request (ARQ) processes, especially synchronousprocesses. There are several ways to handle this. One approach is tosimply shift any required or expected ACK/NACK or scheduled uplinktransmission in time, e.g., by a number of sub-frames equal to thelength of the guard interval. Another approach is to handle scheduleduplink transmissions and/or ARQ feedback in a way similar to thatcurrently specified in LTE standards for measurement gaps. Inparticular, 3GPP TS 36.321 specifies that conflicts between scheduleduplink transmissions and measurement gaps are handled as follows:

-   -   When a configured uplink grant is indicated during a measurement        gap and indicates an UL-SCH transmission during a measurement        gap, the UE processes the grant but does not transmit on UL-SCH.        [ . . . ]    -   NOTE: When no UL-SCH transmission can be made due to the        occurrence of a measurement gap, no HARQ feedback can be        received and a non-adaptive retransmission follows.

In other words, the UL-SCH transmission is cancelled, but thecorresponding HARQ (Hybrid-ARQ) process will perform a non-adaptive HARQretransmission at the next HARQ round-trip-time (RTT). The sameprocedure can be adapted to accommodate conflicts between scheduleduplink transmissions and guard intervals in various embodiments of thepresent invention.

Similarly, conflicts between measurement gaps and HARQ feedback arehandled in TS 36.321 as follows:

-   -   if there is a measurement gap at the time of the HARQ feedback        reception for this transmission and if the MAC PDU was not        obtained from the Msg3 buffer:    -   set HARQ FEEDBACK to ACK at the time of the HARQ feedback        reception for this transmission.

In other words, the HARQ process is suspended if the HARQ feedbackcannot be received.

Again, the same procedure can be adapted to accommodate conflictsbetween HARQ feedback (or other ARQ or error detection/correctionfeedback) in various embodiments of the invention. For example, controlcircuits in any of the base stations and/or mobile stations describedabove may be further configured to automatically delay anautomatic-repeat-request process that is affected by a configurationchange by a number of transmission-time intervals equal to thepre-determined guard interval. Thus, for example, if a base stationwould normally have expected a HARQ retransmission at subframe 5, butthat subframe is now pre-empted by a guard interval of one subframe, thebase station may be configured to adjust the corresponding HARQ processto anticipate the retransmission at subframe 6 instead. In someembodiments, all pending HARQ processes for a given mobile station maybe delayed by an interval equal to the guard interval length.

Similar adjustments may be carried out at the mobile station. Forinstance, some embodiments of the mobile stations discussed above may beconfigured to automatically delay one or more automatic-repeat-requestprocesses by a number of transmission-time intervals equal to thepre-determined guard interval, in response to a configuration change. Insome embodiments, the mobile station's control circuitry may be moregenerally configured to determine that an outgoing data transmission isscheduled for the guard interval and to defer the data transmissionuntil after the pre-determined guard interval. In some cases, this maysimply mean delaying scheduled data transmissions. In other cases, themobile station may be configured to behave as if it had actuallytransmitted the scheduled data at the guard interval. Because no datawas actually sent, the mobile station will subsequently receive a NACK(or may assume that one is received), invoking normal HARQretransmission procedures. Thus, in some embodiments, the deferral ofdata transmission until after the pre-determined guard intervaleffectively comprises performing a HARQ retransmission of the outgoingdata transmission, where the HARQ retransmission is in fact the firsttransmission of the data.

Referring once more to the illustration of a wireless system 300 in FIG.3, those skilled in the art will appreciate that only simplified blockdiagrams of eNodeB 310 and mobile station 320 are provided, as thoseskilled in the art are familiar with the detailed construction of thesenodes and those details are unnecessary to a complete understanding ofthe present invention. While the details of an eNodeB 310 constructedaccording to the current invention will vary, those skilled in the artwill appreciate that an eNodeB 310 configured to carry out one or moreof the scheduling techniques described herein may comprise the basicelements pictured in FIG. 3, including radio circuits 312, configuredaccording to the LTE specifications to communicate with one or moremobile stations, including mobile station 320, and signal processing andcontrol circuits 314, again configured according to LTE specificationsfor communicating with mobile stations and the supporting 3GPP network.Signal processing & control circuits 314 comprises a scheduler function316, configured according to one or more of the techniques describedabove for scheduling uplink and/or downlink transmissions on themultiple carriers (carriers 1 to J) available. Those skilled in the artwill further appreciate that signal processing & control circuits 314and scheduler function 316 may be implemented using one or severalmicroprocessors, digital signal processors, special-purpose digitalhardware, and the like, configured with appropriate software (stored inone or more memory devices, not shown) and/or firmware, as necessary, tocarry out LTE communication protocols and the one or more of theparticular scheduling techniques described above.

Likewise, those skilled in the art will appreciate that the details of amobile station 320 will vary, but that a mobile station 320 configuredto carry out one or more of the techniques described herein may comprisethe basic elements pictured in FIG. 3, including radio circuits 322,configured according to the LTE specifications to communicate with oneor more eNodeBs, such as eNodeB 310. Mobile station 320 furthercomprises baseband processing and control circuits 324, again configuredaccording to LTE specifications for operating within an LTE system andthe supporting 3GPP network. Baseband processing & control circuits 324comprise a DRX/DTX control function 326, configured according to one ormore of the techniques described above. In particular, DRX/DTX function326 generates control signals to activate, de-activate, and/orre-configure portions of radio circuits 322, depending on schedulinginformation received from eNodeB 310 and in accordance withpre-determined scheduling rules that provide for the use of guardperiods to prevent or reduce the need for radio configuration changesduring subframes in which receive or transmit functions are active.

Once more, those skilled in the art will appreciate that basebandprocessing & control circuits 324 and DRX/DTX control function 326 maybe implemented using one or several microprocessors, digital signalprocessors, special-purpose digital hardware, and the like, configuredwith appropriate software (stored in one or more memory devices, notshown) and/or firmware, as necessary, to carry out LTE communicationprotocols and one or more of the DRX/DTX techniques described herein.

Of course, the preceding descriptions of various techniques forimplementing DRX/DTX and other transceiver resource managementfunctionality in a multi-carrier environment are given for purposes ofillustration and example, and those skilled in the art will appreciatethat the methods, apparatus, and systems described above can be readilyadapted for other systems than those specifically described herein.Those skilled in the art will also appreciate, of course, that thepresent invention may be carried out in other ways than thosespecifically set forth herein without departing from essentialcharacteristics of the invention. Accordingly, the exemplary embodimentspresented herein are thus to be considered in all respects asillustrative and not restrictive.

The present invention may, of course, be carried out in other ways thanthose specifically set forth herein without departing from essentialcharacteristics of the invention. The present embodiments are to beconsidered in all respects as illustrative and not restrictive, and allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein.

What is claimed is:
 1. A wireless mobile station configured formulti-carrier operation, the wireless mobile station comprising acontrol circuit configured to: receive, using a first component-carrierconfiguration, signaling information indicating that a change ofconfiguration to a second component-carrier configuration is pending;selectively activate, de-activate, or reconfigure one or moretransceiver components during a pre-determined guard interval of atleast one transmission-time interval, based on the signalinginformation; and receive second data from the base station according tothe second component-carrier configuration, after the guard interval. 2.The wireless mobile station of claim 1, wherein the pre-determined guardinterval comprises at least one subframe.
 3. The wireless mobile stationof claim 1, wherein the pre-determined guard interval immediatelyfollows the transmission-time interval in which the signalinginformation is received.
 4. The wireless mobile station of claim 1,wherein the guard interval is delayed by one or more transmission-timeintervals following the transmission-time interval in which the changeof configuration is signaled, and wherein the control circuit isconfigured to continue receiving the first data according to the firstconfiguration for at least one transmission-time interval subsequent toreceiving the signaling information and prior to the pre-determinedguard interval.
 5. The wireless mobile station of claim 1, wherein thechange of configuration comprises a change in the number of componentcarriers to be used for data transmission or a change to a set of activecomponent carriers, with the number of active component carriersremaining the same.
 6. The wireless mobile station of claim 1, whereinthe control circuit is further configured to delay anautomatic-repeat-request process corresponding to the mobile station bya number of transmission-time intervals equal to the pre-determinedguard interval.
 7. The wireless mobile station of claim 1, wherein thecontrol circuit is further configured to determine that an outgoing datatransmission is scheduled for the guard interval and to defer the datatransmission until after the pre-determined guard interval.
 8. Thewireless mobile station of claim 7, wherein deferring the datatransmission until after the pre-determined guard interval comprisesperforming a HARQ retransmission of the outgoing data transmission.
 9. Amethod in a wireless mobile station configured for multi-carrieroperation, the method comprising: receiving, using a firstcomponent-carrier configuration, signaling information indicating that achange of configuration to a second component-carrier configuration ispending; selectively activating, de-activating, or reconfiguring one ormore transceiver components during a pre-determined guard interval of atleast one transmission-time interval, based on the signalinginformation; and receiving second data from the base station accordingto the second component-carrier configuration, after the guard interval.10. The method of claim 9, wherein the pre-determined guard intervalcomprises at least one subframe.
 11. The method of claim 9, wherein thepre-determined guard interval immediately follows the transmission-timeinterval in which the signaling information is received.
 12. The methodof claim 9, wherein the guard interval is delayed by one or moretransmission-time intervals following the transmission-time interval inwhich the change of configuration is signaled, and wherein the methodfurther comprises receiving the first data according to the firstconfiguration for at least one transmission-time interval subsequent toreceiving the signaling information and prior to the pre-determinedguard interval.
 13. The method of claim 9, wherein the change ofconfiguration comprises a change in the number of component carriers tobe used for data transmission or a change to a set of active componentcarriers, with the number of active component carriers remaining thesame.
 14. The method of claim 9, further comprising delaying anautomatic-repeat-request process corresponding to the mobile station bya number of transmission-time intervals equal to the pre-determinedguard interval.
 15. The method of claim 9, further comprisingdetermining that an outgoing data transmission is scheduled for theguard interval and deferring the data transmission until after thepre-determined guard interval.
 16. The method of claim 15, whereindeferring the data transmission until after the pre-determined guardinterval comprises performing a HARQ retransmission of the outgoing datatransmission.
 17. A method in a base station for controlling datatransmission in a wireless communications network configured formulti-carrier operation, the method comprising: signaling, to a mobilestation using a first component-carrier configuration, a change ofconfiguration from the first configuration to a second component-carrierconfiguration; refraining from transmitting data to the mobile stationduring a pre-determined guard interval of at least one transmission-timeinterval subsequent to the signaling of the change of configuration; andtransmitting second data to the mobile station according to the secondcomponent-carrier configuration, after the guard interval.
 18. Themethod of claim 17, wherein the pre-determined guard interval comprisesat least one subframe.
 19. The method of claim 17, wherein thepre-determined guard interval immediately follows the transmission-timeinterval in which the change of configuration is signaled.
 20. Themethod of claim 17, wherein the guard interval is delayed by one or moretransmission-time intervals following the transmission-time interval inwhich the change of configuration is signaled, and wherein the methodfurther comprises continuing transmission of the first data according tothe first configuration for at least one transmission-time intervalsubsequent to the signaling of the change of configuration and prior tothe pre-determined guard interval.